The organization of organic-capped gold nanoparticles in PS-b-PMMA monolayers is investigated. The preferred location of the particles within the block copolymer template is found to depend on both nanoparticle size and the length of the aliphatic capping agent. In the case of relatively short ligands, the particles behave as hard spheres and their incorporation in the polymer matrix can be qualitatively rationalized by entropic considerations. Three distinct arrangements are observed. Particles that are small, relative to the radius of gyration of the host polymer, evenly disperse within the PS domains, whereas the largest particles are considered form ordered, island-like aggregates. Particles of intermediate size exhibit the most striking arrangement, being relegated to the PS-PMMA interface to form organized ring structures. The tendency of these particles to assemble at the interface is sufficiently strong to force a modification of the polymer morphology to accommodate the particles at higher loadings. As the number of particles is increased, the circular PS-b-PMMA surface micelles elongate to form nanostrands.

The investigation of the Localized Surface Plasmon Resonance for plasmonic nanoparticles has opened new perspectives for optical nanosensors. Today, an issue in plasmonics is the development of large scale and low cost devices. We focus here on the Langmuir-Blodgett technique to self-organize gold nanoparticles (~ 7 nm) into rings (~ 60 nm) via polystyrene-b-polymethylmethacrylate templates. In particular, we investigated the optical properties of organized gold nanoparticle rings over large areas and report experimental evidence for plasmon resonances of both individual nanoparticles and collective modes. This paves the way for designing devices with multiple resonances in the visible-Infra-red spectrum and developing optical sensors.In parallel with progress in characterization techniques, much effort has been made to set up new strategies for smaller metallic nanoparticle synthesis. Two approaches have been developed to synthesize metallic nano-objects: the top-down and the bottom-up ones. The top-down approach consists of taking and etching a massive material down to the desired shape and size. The associated processes, such as Electron Beam Lithography (Haynes et al. 2003) or Focused-Ion-Etching (Tseng 2004), take advantage of high reproducibility in finding immediate applications in the industry. This approach now allows for the fabrication of structures as small as 20 nm in size but it is still challenging to obtain 5-10 nm structures with well-defined edges via these techniques (Pelton et al. 2008). In order to go below this threshold, synthetic routes, like colloidal synthesis (Sun and Xia 2002), based on the bottom-up approach have been developed for about twenty years. The great advantage of this approach is that it provides significant amounts of nano-objects with dimensions smaller than 20 nm or even 10 nm (Soumare et al 2009). Nevertheless, for the moment, large-scale applications are still limited with this approach due to the difficulty of organizing such metallic nano-objects over large areas. Therefore, a big challenge today is to develop routes for organizing colloids onto substrates, especially for non magnetic nanoparticles (Maurer et al. 2007). Among the most appealing strategies for industrial applications, is that based on the use of block copolymers since they exhibit an exceptional ability to self-organize into microphase-separated domains with controlled shapes and sizes (Fahmi et al. 2009;Kim et al. 2004). Indeed for lithography, block copolymers can provide not only long-range ordered templates but also small feature size and a large variety of patterns, ranging from spheres to lamellar shapes (Tseng and Darling 2010, Krausch andMagerle 2002). The Reactive Ion Etching (RIE) rate of polymethylmethacrylate (PMMA) is sufficiently lower for CF 4 or O 2 gas compared to that of polystyrene (PS) to allow the selective removal of PMMA in PS-b-PMMA block copolymer templates Hiraoka 2002, Asakawa andFujimoto 2005). It has also been shown for PS-b-PMMA block copolymer templates that PMMA can be...

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